Value Of

Format: ? x

Arguments: (node) x Name of an existing node

Returns: [any] The value of the constant x from a previous evaluation or null if unevaluated

Description: The Value Of operator is used to find the value assigned to a node without forcing the node to be evaluated. Note that function-style nodes, such as F(x):=x*x, do not retain their value from previous evaluations, so the Value Of operator will always return null for these nodes. Functions without arguments, such as F():=x*x, and constants, such as F:=x*x, do retain their values.

Examples: Node:=2+3 = creates a new node

?Node = null  (Node not yet evaluated)

Node = 5  (causes Node to evaluate)

?Node = 5  (value from last evaluation)

See Also: reset, clear